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Unformatted text preview: EE 243: ADVANCED IC PROCESSING AND LAYOUT Sp 2008 Homework Assignment #8 (Due April 16, Wed) Reading Assignment : PDG Chapter 9 Lec Notes Problem 1 Vacuum Units and CVD Deposition Parameters A CVD tube reactor operating at 1 atmospheric pressure has a cross-sectional area of 50 cm 2 . The input gas mixture is 2% SiCl 4 , 98%H 2 by volume. The total input gas flow rate is 1.5 liters/min at room temperature. The temperature in the reaction zone is 1250°C with the viscosity of the gas mixture = 3 × 10-4 gm/cm- sec. (a) Assuming flow velocity is uniform across the tube cross-section, estimate the gas stream velocity U at the reaction zone. (b) Calculate the Reynolds number ( ρ UL µ ) for a 3-inch diameter wafer inside the reactor tube. (c) Calculate the concentration of SiCl 4 in the reacting zone (in molecules/cm 3 ) (d) Estimate the Si film growth rate, assuming the growth process is mass-transfer limited and the gas diffusivity D G is ≈ 8 cm 2 /sec . Problem 2 CVD Deposition Rate - Effect of Carrier Gas Poly-Si deposition by pyrolysis of silane will have deposition rate dependence on both the carrier gas and...
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- Spring '03
- Chemical vapor deposition